Visual processing of contours and textures

点击翻译按钮获取中文摘要

This application is for funds to continue and develop my research into the visual brain mechanisms involved in processing contours and textures, using psychophysics and brain imaging as techniques.  Contours and textures are critical components of objects, and so an understanding of how contours and textures are handled by the brain is essential to our understanding of how objects are recognised. I have recently developed a novel technique for studying human contour/texture shape perception, using contours that have a sinusoidal shape profile (ones that 'wiggle' up and down across space with a given frequency, or 'shape-frequency'). If one adapts to one of these contours by staring at it for a minute or so, the perceived shape-frequency of a subsequently viewed contour with a slightly different physical shape-frequency is shifted in a direction away from that of the adaptation shape-frequency. I call this the 'shape-frequency after-effect', or SFAE.  By measuring SFAEs for adaptation-test combinations that have identical characteristics in terms of their motion, depth, colour etc., and compare these with SFAEs obtained from adaptation-test combinations with different characteristics (such as having different directions of motion, different colours etc.), I can determine how specific are contour-shape mechanisms for a whole range of characteristics.  This in turn will enable me to test between two hypotheses as to how the brain computes shape: does it use a highly reduced, cartoon-like sketch of an object, or is shape computed from a much richer object representation ?   My psychophysical studies of contour-shape processing will be extended to texture-shape processing and complemented by brain imaging studies using fMRI.